The determination of salicylate in biological fluids such as human serum, has diagnostic significance. Acetylsalicylic acid (aspirin) is used as an analgesic and as an anti-inflammatory drug for arthritis. It rapidly hydrolyzes to salicylate which has the therapeutic effect and a long half life. The therapeutic level as an analgesic is up to 20 mg/dl. For arthritis the level is up to 30 mg/dl. Problems such as headaches, tinnitus, flushing and hyperventilation occur at higher salicylate levels followed by imbalances in the acid-base level. Salicylate levels above 60 mg/dl can be lethal.
U.S. Pat. No. 4,416,983 discloses a solution method for the determination of salicylate in body serums. The method is based on the following 2 chemical reactions: ##STR1## The method is carried out on a multilayer dry element disclosed in U.S. Pat. No. 5,185,249. The problem is that salicylate assay results are biased by the presence of albumin in serum samples. Albumin binds to salicylate thereby preventing its participation in the reaction described above. One approach to release salicylate from the albumin is to reduce sample pH. This is not possible in the dry test element disclosed in U.S. Pat. No. 5,185,249 because that element must also operate at the pH optimum of the enzymes used in the element.